HashService.php

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<?php
namespace TYPO3\CMS\Extbase\Security\Cryptography;

class HashService implements \TYPO3\CMS\Core\SingletonInterface {

    public function generateHmac($string) {
        if (!is_string($string)) {
            throw new \TYPO3\CMS\Extbase\Security\Exception\InvalidArgumentForHashGenerationException('A hash can only be generated for a string, but "' . gettype($string) . '" was given.', 1255069587);
        }
        $encryptionKey = $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'];
        if (!$encryptionKey) {
            throw new \TYPO3\CMS\Extbase\Security\Exception\InvalidArgumentForHashGenerationException('Encryption Key was empty!', 1255069597);
        }
        return hash_hmac('sha1', $string, $encryptionKey);
    }

    public function appendHmac($string) {
        $hmac = $this->generateHmac($string);
        return $string . $hmac;
    }

    public function validateHmac($string, $hmac) {
        return $this->generateHmac($string) === $hmac;
    }

    public function validateAndStripHmac($string) {
        if (!is_string($string)) {
            throw new \TYPO3\CMS\Extbase\Security\Exception\InvalidArgumentForHashGenerationException('A hash can only be validated for a string, but "' . gettype($string) . '" was given.', 1320829762);
        }
        if (strlen($string) < 40) {
            throw new \TYPO3\CMS\Extbase\Security\Exception\InvalidArgumentForHashGenerationException('A hashed string must contain at least 40 characters, the given string was only ' . strlen($string) . ' characters long.', 1320830276);
        }
        $stringWithoutHmac = substr($string, 0, -40);
        if ($this->validateHmac($stringWithoutHmac, substr($string, -40)) !== TRUE) {
            throw new \TYPO3\CMS\Extbase\Security\Exception\InvalidHashException('The given string was not appended with a valid HMAC.', 1320830018);
        }
        return $stringWithoutHmac;
    }
}